Mazda reveals i-ELOOP capacitor-based regenerative braking system

Batteries aren't the only technology mankind has invented to store electricity, and Mazda is working on a solution to the energy storage needs of electrified vehicles with a new system it's calling i-ELOOP. While we wish it didn't have such a cumbersome moniker, the technology behind i-ELOOP is intriguing.

Mazda claims that its i-ELOOP system will be featured in the first production passenger vehicle with recaptured energy from regenerative braking stored in a capacitor. The rest of the bits and pieces behind the tech include a variable voltage alternator and a DC/DC converter that sends energy otherwise lost to heat in the brakes at up to 25 volts to the Electric Double Layer Capacitor, where it's stored for later use.

There's no electric motor in the i-ELOOP drivetrain, so the capacitor releases its energy to recharge the car's battery and to help power electric components like the heating and air conditioning systems. All in, Mazda promises fuel savings of up to 10 percent over cars not equipped with regenerative braking. Read all about it in the press release after the break.

Hiroshima, Japan 25 November 2011. Mazda Motor Corporation has developed the world's first passenger vehicle regenerative braking system that uses a capacitor. The groundbreaking system, which Mazda calls 'i-ELOOP', will begin to appear in Mazda's vehicles in 2012. In real-world driving conditions with frequent acceleration and braking, 'i- ELOOP' improves fuel economy by approximately 10 percent.

Mazda's regenerative braking system is unique because it uses a capacitor, which is an electrical component that temporarily stores large volumes of electricity. Compared to batteries, capacitors can be charged and discharged rapidly and are resistant to deterioration through prolonged use. 'i-ELOOP' efficiently converts the vehicle's kinetic energy into electricity as it decelerates, and uses the electricity to power the climate control, audio system and numerous other electrical components.

Regenerative braking systems are growing in popularity as a fuel saving technology. They use an electric motor or alternator to generate electricity as the vehicle decelerates, thereby recovering a portion of the vehicle's kinetic energy. Regenerative braking systems in hybrid vehicles generally use a large electric motor and dedicated battery.

Mazda examined automobile accelerating and decelerating mechanisms, and developed a highly efficient regenerative braking system that rapidly recovers a large amount of electricity every time the vehicle decelerates. Unlike hybrids, Mazda's system also avoids the need for a dedicated electric motor and battery.

'i-ELOOP' features a new 12-25V variable voltage alternator, a low-resistance electric double layer capacitor and a DC/DC converter. 'i-ELOOP' starts to recover kinetic energy the moment the driver lifts off the accelerator pedal and the vehicle begins to decelerate. The variable voltage alternator generates electricity at up to 25V for maximum efficiency before sending it to the Electric Double Layer Capacitor (EDLC) for storage. The capacitor, which has been specially developed for use in a vehicle, can be fully charged in seconds. The DC/DC converter steps down the electricity from 25V to 12V before it is distributed directly to the vehicle's electrical components. The system also charges the vehicle battery as necessary. 'i-ELOOP' operates whenever the vehicle decelerates, reducing the need for the engine to burn extra fuel to generate electricity. As a result, in "stop-and-go" driving conditions, fuel economy improves by approximately 10 percent.

The name 'i-ELOOP' is an adaptation of "Intelligent Energy Loop" and represents Mazda's intention to efficiently cycle energy in an intelligent way.

'i-ELOOP' also works in conjunction with Mazda's unique 'i-stop' idling stop technology to extend the period that the engine can be shut off.

Mazda is working to maximize the efficiency of internal combustion engine vehicles with its groundbreaking SKYACTIV TECHNOLOGY. By combining this with i-stop, i-ELOOP and other electric devices that enhance fuel economy by eliminating unnecessary fuel consumption, Mazda is striving to deliver vehicles with excellent environmental performance as well as a Zoom-Zoom ride to all its customers.

At the 42nd Tokyo Motor Show, Mazda will debut the i-ELOOP system in the TAKERI concept car, a next generation mid-sized sedan that features SKYACTIV TECHNOLOGY and KODO – Soul of Motion design theme.

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This is actually a really cool idea. Assuming the components weight less than 100lbs and cost less than $300 - both of which seem perfectly reasonable - I hope they manage to put these into all of their non-hybrid cars.

Well with the way the EPA tests cars, it would seem that in the USA there would be no benefit because the in town mileage would not go up.
In real world driving this would benefit drivers from between 5-10% improvement since no gas would be burned when idled at a stop light.
Either way, I would like to see the i-stop & i-loop sold to consumers as their fuel economy package (of some sort) which could be installed at the dealer, if not installed in the factory.

EPA tests don't take idling into account? Sounds like a job for Mazda marketing to rectify. Regardless, it's awesome to see my favourite mainstream manufacturer doing whatever it can to beat the competition.

25V?
You can't store much in a capacitor. Let's say this is a 4 Farad capacitor (unlikely given the physical size that would be).
At 25V you could store 25*25*4/2 or 1250 Joules.
The battery in an iPhone stores about 5.3Wh, or 19,080 Joules. That's about 15x as much. And it's about 1/100th the size of a 4F (25V rated) cap.

I found a 5000 F 2.5 V capacitor on Digikey the size of a coke can. Model: B49410B2506Q000 That holds 30 kJ of energy, which is approximately what the Mazda has at around 7 m / s or about 15 mph. So, 4 of them could hold the energy of the car going at 30 mph, a common speed in the city.

I'm not sure that energy savings will be very substantial if they are just putting that voltage into the battery, what charges those capacitors? why not just put the power back into whatever generated it? a generator backwards is an electric motor :)

[blocked]

Interesting tech - though I wonder if the system is incorporated like a hybrid's battery, and if it'll be expensive to replace (if/when needed). It would really be cool to see if this system can be expanded to hold enough juice to suit a mild hybrid like Honda's IMA system.

I would expect that it might be expensive to replace. That being said, ultracaps have a cycle life ranging in the millions, and are not very temperature sensitive. Meaning that even if they end up being expensive to replace, they should last the lifetime of the vehicle (or at least longer than things like transmissions, which are also expensive).

Unfortunately the energy density of super capacitors is really too small to make too much sense. In this case the capacitor is holding 25,000 Joules of energy.
Just for comparison…
A Tesla Model S 85kWh battery holds 306,000,000 Joules of energy. That's above 12,000 times more capacity than Mazda's solution. If you assume otherwise similar conditions, that capacitor of Mazda represents about 1.3 seconds of driving at 60mph of energy consumption at 60mph.
ONE SECOND OF ENERGY…LOL…SILLY

Read an electrical schematic and you will see that a battery and a capacitor have the same symbol, because they're the same thing. Nothing shocking about storing your braking energy, but it is surprising that Mazda's devised a test that can actually make it appear to save you 10% of your fuel. Sound's bogus to me if the only use of that juice it to power your sparks, and some ancillaries. My guess is they built it with and without the Cap, saw zero difference and decided to keep the cap for marketing.
BTW, ultra-capacitors will shut down the battery industry for EVs overnight when they crack it. And the ICE industry as well, so best to support those UC geeks now.

1. They are not the same symbol.
2. They are not the same thing
3. And how big would a 1.4 kWh capacitor? Take 10 125V Maxwell Ultracaps = 1.4 kWh.
4. They can't compete with batteries, particularly Li-Ion, let alone "shut down" the industry
5. They'll shut down the ICE industry?! 1.4kWh = 1 quart of gasoline burnt in an ICE.
6. Based on everything you've said I doubt your name is even Karl

Super Caps will almost certainly never rival batteries because they use "static charge accumulation" rather than red-ox reactions to store charge (there is an exception called psuedocapacitors but I guarantee this is over your head as there is no Wikipedia article on it). The concept of a capacitor, even ones that make use of chemistry, is physical and you'd likely go over the basics in an undergraduate freshman physics course, batteries you don't really delve into until an upper level physical chemistry course and for good reason. The deeper scientific concepts behind the two are quite complicated and with enough analysis one might say they are related. You, KarllnSanDiego, really lack the expertise to make this inference and calling them the same shows a great deal of ignorance. What's interesting though is I'm currently doing research on combining the technology of an EDLC and a battery...I'm not really allowed to go into that anymore.
Perhaps the biggest observable difference between the two is as a capacitor discharges it's voltage decreases (usually linearly) making it very difficult to use for the high energy applications that batteries are used for. This is why the variable voltage alternator is required. Where capacitors excel is high power applications (ex. starting a tank!). Mazda has very smartly suggested this technology for quickly capturing regenerative break energy and my theory is we will see it on their CX-5 this year (I sure hope I'm right!).
The idea to use this technology is a dime a dozen however companies that act on such ideas are rare, which is why I hope Mazda pulls through.
Source: university capacitor research lab..maybe doing work for Maxwell.